In January, Mill joined Jay-Z and others to form a coalition that lobbies for changes to state probation and parole laws called the Reform Alliance.

Mill became a symbol for criminal justice reform activists after a judge in Pennsylvania sentenced him to two to four years in prison for minor violations of his probation conditions in a decade-old gun and drug possession case. He spent months in prison before a court ordered him released.

Mill said at Thursday's announcement that he's trying to "give young kids a fair shot in the system."